Muricatetrocins A and B and Gigantetrocin B: Three New Cytotoxic Monotetrahydrofuran‐Ring Acetogenins from Annona muricata

Extracts from the seeds of Annona muricata yielded three new Annonaceous acetogenins: muricatetrocin A (= (5 S )‐3‐{(2 R )‐2‐hydroxy‐9‐{(2 R ,5 S )‐tetrahydro‐5‐[(1 S ,4 S ,5 S )‐1,4,5‐trihydroxyheptadecyl]furan‐2‐yl}nonyl}‐5‐methylfuran‐2(5 H )‐one; 1 ), muricatetrocin B (= (5 S )‐{(2 R )‐2‐hydroxy‐9‐{(2 S ,5 S )‐tetrahydro‐5‐[(1 S ,4 S ,5 S )‐1,4,5‐trihydroxyheptadecyl]furan‐2‐yl}nonyl}‐5‐methylfuran‐2(5 H )‐one; 2 ), and gigantetrocin B (= (5 S )‐3‐{(2 R )‐2‐hydroxy‐7‐{(2 S ,5 S )‐tetrahydro‐5‐[(1 S ,4 R ,5 R )‐1,4,5‐trihydroxynonadecyl]furan‐2‐yl}heptyl}‐5‐methyl‐furan‐2(5 H )‐one; 3 ). Their C‐skeletons were deduced by mass spectrometry. Configurations were determined by 1 H‐NMR of ketal derivatives and 2D‐NMR experiments utilizing Mosher esters. A previously described compound, gigantetrocin A (= (5 S )‐3‐{(2 R )‐2‐hydroxy‐7‐{(2 S ,5 S )‐tetrahydro‐5‐[(1 S ,4 S ,5 S )‐1,4,5‐trihydroxynonadecyl]furan‐2‐yl}heptyl}‐5‐methylfuran‐2‐(5 H )one; 4 ), was also isolated and is new to this species. Compounds 1–4 were all selectively cytotoxic for the HT‐29 human colon‐tumor cell line with potencies at least 10 times that of adriamycin.